Personally, I use the Curse Client to update most of my addons, since most addons are published both here and on Curse. For the few addons that aren't on Curse, I add them to my WoWI favorites list so I can see when they are updated. If you don't visit the site often, you can enable email notifications when anything on your favorites list is updated (click the Preferences link on the left on your favorites list), or subscribe to the RSS feed for your favorites list (click the RSS button at the top of your favorites list). If you don't know what RSS feeds are, just use the email option.